4 files changed, 4 insertions, 4 deletions
diff --git a/Makefile b/Makefile
index c1249fa..0bf0eb7 100644
--- a/Makefile
+++ b/Makefile
@@ -29,7 +29,7 @@ INSTALL ?= install
 MKDIR ?= mkdir -p
 RM ?= rm -f
 
-WFLAGS ?= -Wall -Wmissing-declarations
+WFLAGS ?= -Wall -Wmissing-declarations -Wstrict-prototypes
 CFLAGS ?= -g $(WFLAGS)
 LDFLAGS ?=
 DEPFLAGS ?= -MD -MP -MF $(@:.o=.d)
diff --git a/main.c b/main.c
index 3c19092..066061d 100644
--- a/main.c
+++ b/main.c
@@ -28,7 +28,7 @@
  * future open() calls may use those file descriptors, and std{in,out,err} will
  * use them unintentionally.
  */
-static int open_std_streams() {
+static int open_std_streams(void) {
 #ifdef O_PATH
 	const int inflags = O_PATH, outflags = O_PATH;
 #else
diff --git a/printf.c b/printf.c
index 595e9dd..b13f43f 100644
--- a/printf.c
+++ b/printf.c
@@ -420,7 +420,7 @@ static void free_directive(struct bfs_printf_directive *directive) {
 /**
  * Create a new printf directive.
  */
-static struct bfs_printf_directive *new_directive() {
+static struct bfs_printf_directive *new_directive(void) {
 	struct bfs_printf_directive *directive = malloc(sizeof(*directive));
 	if (!directive) {
 		perror("malloc()");
diff --git a/util.c b/util.c
index 1e5ebdb..2a01af1 100644
--- a/util.c
+++ b/util.c
@@ -272,7 +272,7 @@ bool is_nonexistence_error(int error) {
 }
 
 /** Read a line from standard input. */
-static char *xgetline() {
+static char *xgetline(void) {
 	char *line = dstralloc(0);
 	if (!line) {
 		return NULL;